Signal processing circuit and sensor unit

Abstract

The technical problem of the present invention is to provide a signal processing circuit capable of reducing power consumption. This signal processing circuit processes a detection signal that is output from a sensor and includes a DC component and an AC component, and is provided with: a low-pass filter that extracts the DC component from the detection signal; and a high-pass filter that extracts an AC component from the detection signal.

Description

Technical Field

[0001] The present disclosure relates to a signal processing circuit and a sensor unit. Background Art

[0002] In order to improve the detection accuracy of the sensor, various signal processing is sometimes performed on the detection signal output from the sensor. For example, Patent Document 1 discloses a signal processing circuit that can improve the detection accuracy by amplifying the output signal from the magnetic sensor.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-180727 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, due to the detection signal output from the sensor and input to the signal processing circuit, and the signal processing performed on the detection signal, the power consumption consumed in the signal processing may increase. For example, in a magnetic sensor, in order to detect the detected magnetism with high accuracy when the sensitivity of the sensor is low, the detection signal is amplified. In the signal processing such as amplification processing, the power consumption may increase due to the signal that becomes the object of the signal processing.

[0008] The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a signal processing circuit capable of reducing power consumption.

[0009] Technical solutions to the problem

[0010] A signal processing circuit according to one embodiment of the present disclosure processes a detection signal output from a sensor and including a DC component and an AC component, and includes a low-pass filter for extracting the DC component from the detection signal and a high-pass filter for extracting the AC component from the detection signal.

[0011] The signal processing circuit according to one aspect of the present disclosure may include a signal adding unit that adds the DC component extracted by the low-pass filter and the AC component extracted by the high-pass filter.

[0012] The signal processing circuit according to one aspect of the present disclosure may include a signal correction unit that corrects the added signal by applying a correction value calculated based on a DC component to the added signal, which is an output signal from the signal adding unit.

[0013] A signal processing circuit according to one aspect of the present disclosure may include: a first signal processing unit that performs a first signal processing on a DC component; and a second signal processing unit that performs a second signal processing on an AC component.

[0014] In the signal processing circuit according to one embodiment of the present disclosure, the sensor may be a magnetic sensor.

[0015] A sensor unit according to one aspect of the present disclosure includes a sensor and a signal processing circuit formed integrally with the sensor.

[0016] Effects of the Invention

[0017] According to the present disclosure, it is possible to provide a signal processing circuit that can reduce power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a block diagram showing a schematic configuration of the sensor unit 100 according to the present embodiment.

[0019] Figure 2 It is a schematic perspective view of the sensor unit 100 according to the present embodiment.

[0020] Figure 3 : is a circuit diagram showing a schematic configuration of the magnetic detection unit 10 according to the present embodiment.

[0021] Figure 4 It is a perspective view showing a schematic structure of the magnetoresistive effect element 14 according to the present embodiment.

[0022] Figure 5 : is a circuit diagram showing a schematic configuration of the magnetic detection unit 10 according to the present embodiment.

[0023] Figure 6 : is a functional block diagram showing the structure of the sensor unit 100 according to the present embodiment.

[0024] Figure 7 It is a diagram showing an example of a signal waveform according to the present embodiment.

[0025] Fig. 8A It is a diagram showing the frequency characteristics of a signal according to this embodiment.

[0026] Figure 8B It is a diagram showing the frequency characteristics of a signal according to this embodiment.

[0027] Figure 8C It is a diagram showing the frequency characteristics of a signal according to this embodiment.

[0028] Fig. 9 : is a functional block diagram showing the structure of the sensor unit 100 according to the present embodiment.

[0029] Fig.10 It is a diagram showing the frequency characteristics of a signal according to this embodiment.

[0030] Fig.11 : is a functional block diagram showing the structure of the sensor unit 100 according to the present embodiment.

[0031] Fig.12 It is a diagram schematically showing an example of the characteristics of the magnetic detection unit 10 according to the present embodiment.

[0032] Fig.13 It is a diagram schematically showing an example of the characteristics of the magnetic detection unit 10 according to the present embodiment.

[0033] Description of Reference Numerals

[0034] 10 Magnetic detection unit

[0035] 12 Components

[0036] 14 Magnetoresistance effect element

[0037] 16 Connection Layer

[0038] 20 Signal Processing Circuit

[0039] 22 Separation circuit

[0040] 22a Low pass filter

[0041] 22b High-pass filter

[0042] 24 Amplifier Circuit

[0043] 24a First amplifier circuit (first signal processing unit)

[0044] 24b Second amplifier circuit (second signal processing unit)

[0045] 26 Adding circuit (signal adding section)

[0046] 28 Correction circuit (signal correction unit)

[0047] 100 sensor units

[0048] 142 Antiferromagnetic layer

[0049] 144 Magnetization fixed layer

[0050] 146 Gap Layer

[0051] 148 Free Layer DETAILED DESCRIPTION

[0052] Hereinafter, an embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described with reference to the accompanying drawings. In addition, in the drawings attached to this specification, for the sake of convenience of illustration and understanding, the scale and the aspect ratio of the dimensions are sometimes appropriately changed and exaggerated from the scale and the aspect ratio of the actual object.

[0053] Hereinafter, as a signal processing circuit of an embodiment of the present disclosure, a signal processing circuit for processing a signal detected by a magnetic sensor is described as an example. However, the signal processing circuit of the embodiment of the present disclosure can also be used for signal processing other than signals detected by a magnetic sensor. The signal processing circuit of this embodiment can also be used for signal processing of signals detected by sensors other than magnetic sensors, for example.

[0054] In the following, in each of the accompanying drawings, the X-axis, Y-axis and Z-axis are sometimes indicated. The X-axis, Y-axis and Z-axis form a three-dimensional orthogonal coordinate system of a right-hand system. In the following, the arrow direction of the X-axis is sometimes referred to as the +X direction, and the direction opposite to the arrow is referred to as the -X direction. The same applies to other axes. In addition, the +Z direction and the -Z direction are sometimes referred to as the "upper side" or even "above", and the "lower side" or even "below", respectively. In addition, the Z-axis direction is sometimes referred to as the "stacking direction". In addition, the planes orthogonal to the X-axis, Y-axis, or Z-axis are sometimes referred to as YZ planes, ZX planes, or XY planes. However, these directions are directions used for convenience in order to illustrate relative positional relationships. Therefore, these directions do not define absolute positional relationships.

[0055] In addition, the following terms and / or values ​​indicating shape and / or geometric conditions do not need to strictly follow their definitions, and can also be interpreted as terms and / or values ​​including a range of degrees that can expect the same function. For example, "parallel" and / or "orthogonal" etc. conform to the above terms. In addition, "length value" and / or "angle value" etc. conform to the above values.

[0056] In addition, when a certain structure is expressed as being "above", "below", "upper side", "lower side", "above", or "below" another structure, it may also include: a certain structure is directly connected to the other structure, and a certain structure is included between the other structure. In other words, the method of including another structure between the other structure can also be expressed as a certain structure being indirectly connected to the other structure. In addition, the expression of "above", "upper side", or "above" can be interchangeable with the expression of "below", "lower side", or "below". In other words, the up and down directions can also be reversed. In addition, the same applies to the left and right.

[0057] In addition, when the same parts and / or parts having the same functions are marked with the same reference numerals or similar reference numerals, repeated descriptions are sometimes omitted. In addition, the dimensional ratios of the drawings are sometimes different from the actual ratios. In addition, a part of the structure of the embodiment is sometimes omitted from the drawings.

[0058] Figure 1 1 is a block diagram showing a schematic structure of the sensor unit 100 according to the present embodiment. Figure 1 As shown, the sensor unit 100 of this embodiment includes: a magnetic detection unit 10 (also referred to as a "magnetic sensor" in this embodiment), and a signal processing circuit 20. The magnetic detection unit 10 outputs a magnetic signal S by applying a magnetic field. The signal processing circuit 20 processes the magnetic signal S input from the magnetic detection unit 10. The signal processing circuit 20 performs signal processing on the magnetic signal S and outputs a signal S'.

[0059] In this embodiment, the magnetic detection unit 10 may be, for example, a TMR (tunnel magnetoresistance effect) element. The magnetic detection unit 10 is not limited to a TMR element, but may be a GMR (giant magnetoresistance effect) element, an AMR (anisotropic magnetoresistance effect) element, a Hall element, or other types of magnetic detection elements.

[0060] Figure 2 is a schematic perspective view of the sensor unit 100. Figure 2 As shown, the magnetic detection unit 10 is formed on the signal processing circuit 20 (+Z direction). A terminal group 62 is provided on the upper surface 10s of the magnetic detection unit 10, and a terminal group 64 is provided on the upper surface 20s of the signal processing circuit 20. The terminal group 62 of the magnetic detection unit 10 and the terminal group 64 of the signal processing circuit 20 are connected to each other, for example, by a plurality of bonding wires 50. The magnetic detection unit 10 may also be configured to detect an external magnetic field, for example.

[0061] Figure 3 1 is a circuit diagram showing a schematic structure of the magnetic detection unit 10. Figure 3 As shown, the magnetic detection unit 10 has, for example, one or more element units 12. Figure 3 In the example shown, the magnetic detection unit 10 includes a first element unit 12a, a second element unit 12b, a third element unit 12c, and a fourth element unit 12d. The plurality of element units 12 of the magnetic detection unit 10 may form a Wheatstone bridge circuit.

[0062] Figure 41 is a perspective view showing a schematic structure of a magnetoresistance effect element 14 (hereinafter also referred to as "MR element") included in the element unit 12. The element unit 12 includes, for example, a plurality of magnetoresistance effect elements 14 connected in series, and each of the plurality of magnetoresistance effect elements 14 may be, for example, a spin valve type magnetoresistance effect element. Figure 4 As shown, in this embodiment, the magnetoresistance effect element 14 may have a substantially elliptical shape, for example. In this embodiment, the magnetoresistance effect element 14 may be connected to the element portion 12 via a plurality of connection layers 16 .

[0063] like Figure 4 As shown, for example, the first connection layer 16a of the plurality of connection layers 16 is in contact with the bottom surfaces of two adjacent MR elements 14 in the circuit structure to electrically connect these MR elements 14. In addition, the second connection layer 16b is in contact with the top surfaces of adjacent MR elements 14 to electrically connect these MR elements 14.

[0064] In addition, if Figure 4 As shown, the MR element 14 includes an antiferromagnetic layer 142, a magnetization fixed layer 144, a gap layer 146, and a free layer 148. Figure 4 As shown, the antiferromagnetic layer 142 is electrically connected to the first connection layer 16a, and the free layer 148 is electrically connected to the second connection layer 16b. The antiferromagnetic layer 142 includes an antiferromagnetic material. The antiferromagnetic layer 142 can also generate exchange coupling with the magnetization fixed layer 144 to fix the magnetization direction of the magnetization fixed layer 144.

[0065] The spin valve type MR element 14 is, for example, a TMR element or a GMR element. When the MR element is a TMR element, the gap layer 146 is, for example, a tunnel barrier layer. When the MR element is a GMR element, the gap layer 146 is, for example, a non-magnetic conductive layer. In addition, the configuration of the antiferromagnetic layer 142, the magnetization fixed layer 144, the gap layer 146, and the free layer 148 of the MR element 14 is not limited to Figure 4 For example, the antiferromagnetic layer 142, the magnetization fixed layer 144, the gap layer 146, and the free layer 148 may also be arranged in the Z direction in a manner similar to that of FIG. Figure 4 The example shown is stacked in the reverse order.

[0066] In the spin valve type magnetoresistive effect element 14, the resistance value changes according to the angle between the magnetization direction of the free layer 148 and the magnetization direction of the magnetization fixed layer 144. When the angle is 0°, the resistance value is the minimum value, and when the angle is 180°, the resistance value is the maximum value.

[0067] For example, as referenced Figure 3It can also be that the magnetic detection unit 10 includes: a first element unit 12a, a second element unit 12b, a third element unit 12c and a fourth element unit 12d as multiple element units 12, and a full-bridge Wheatstone bridge circuit is formed by the first element unit 12a, the second element unit 12b, the third element unit 12c and the fourth element unit 12d. Figure 3 The Wheatstone bridge circuit shown includes: a power port V, a ground port G, and output ports E1 and E2. A voltage of a predetermined magnitude is applied to the power port V, and the ground port G is grounded. Alternatively, one end of the first element portion 12a is connected to the power port V, and the other end of the first element portion 12a is connected to the output port E1. Alternatively, one end of the second element portion 12b is connected to the output port E1, and the other end of the second element portion 12b is connected to the ground port G. Similarly, one end of the third element portion 12c is connected to the ground port G, and the other end of the third element portion 12c is connected to the output port E2. Alternatively, one end of the fourth element portion 12d is connected to the output port E2, and the other end of the fourth element portion 12d is connected to the power port V.

[0068] In this embodiment, for example, the magnetization direction of the magnetization fixed layer 144 of the magnetoresistive effect element 14 is fixed in a direction parallel to the X axis. Figure 3 As shown by the arrows in the middle, for example, the magnetization direction of the magnetization fixed layer 144 of the magnetoresistance effect element 14 of the first element portion 12a and the third element portion 12c is the "+X direction", and the magnetization direction of the magnetization fixed layer 144 of the magnetoresistance effect element 14 of the second element portion 12b and the fourth element portion 12d is the "-X direction". The magnetization direction of the magnetization fixed layer 144 of the magnetoresistance effect element 14 of the first to fourth element portions 12a to 12d is parallel to the short diameter direction or the short side direction of the magnetoresistance effect element 14 of the substantially elliptical or substantially rectangular shape in a plan view, and therefore, the sensitivity axis of the magnetoresistance effect element 14 of the first to fourth element portions 12a to 12d is parallel to the X axis.

[0069] On the other hand, in this embodiment, the magnetization direction of the free layer 148 of the magnetoresistive element 14 in the initial state when the magnetic field to be detected is not applied by the magnetic detection unit 10 may be parallel to the Y axis. Figure 3 In the illustrated embodiment, the easy magnetization axis direction of the free layer 148 of the magnetoresistance effect element 14 of the first element portion 12a and the fourth element portion 12d is the "-Y direction", and the easy magnetization axis direction of the free layer 148 of the magnetoresistance effect element 14 of the second element portion 12b and the third element portion 12c is the "+Y direction". In this embodiment, for example, the easy magnetization axis direction of the free layer 148 of the magnetoresistance effect element 14 of the first to fourth element portions 12a to 12d is parallel to the major axis direction of the magnetoresistance effect element 14 of a substantially elliptical shape when viewed from above.

[0070] In this embodiment, Figure 3 In the magnetic detection unit 10 shown, as a magnetic field is applied to each magnetoresistance effect element 14 of the first to fourth element parts 12a to 12d, the potential difference between the output ports E1 and E2 changes, and the differential detector not shown outputs a signal S corresponding to the potential difference between the output ports E1 and E2 as a signal representing the magnetic field strength to the signal processing unit 20.

[0071] In addition, if Figure 5 As shown, the magnetic detection unit 10 can also form a half-bridge Wheatstone bridge circuit. Figure 5 As shown in FIG. 1 , the magnetic detection unit 10 includes two element units (a first element unit 12a and a second element unit 12b). Figure 5 As shown, one end of the first element portion 12a may be connected to the power port V, the other end of the first element portion 12a may be connected to the output port E1, one end of the second element portion 12b may be connected to the output port E1, and the other end of the second element portion 12b may be connected to the ground port G.

[0072] Hereinafter, the signal processing unit 20 of the sensor unit 100 will be described as an example of the signal processing circuit according to the present embodiment. Figure 6 : is a functional block diagram showing the structure of the sensor unit 100 of the present embodiment. The signal processing unit 20 of the present embodiment is a signal processing circuit that processes the detection signal S output from the magnetic detection unit 10 as a sensor. As described below, in the present embodiment, the detection signal S output from the magnetic detection unit 10 includes a DC component and an AC component. In addition, the signal processing unit 20 includes: a low-pass filter 22a that extracts the DC component from the detection signal S, and a high-pass filter 22b that extracts the AC component from the detection signal S. Therefore, in the present embodiment, the separation circuit 22 of the signal processing circuit 20 has a low-pass filter 22a and a high-pass filter 22b. The signal processing circuit 20 may also have an amplifier circuit 24. The amplifier circuit 24 will be described later.

[0073] In addition, Figure 6 2 shows an example of inputting X-component, Y-component and Z-component signals (Sx, Sy and Sz respectively) from the magnetic detection unit 10 to the signal processing circuit 20. Figure 6 In the embodiment, the magnetic detection unit 10 includes the first magnetic detection unit 10a, the second magnetic detection unit 10b, and the third magnetic detection unit 10c described above.

[0074] In addition, in the present embodiment, the DC component of the detection signal may also include components of frequencies other than the component with a frequency of zero. For example, in addition to the component with a frequency of zero, it may also include components of a specified frequency band with a frequency of 1 or more. For example, the DC component of the detection signal in the present embodiment may also include components with a frequency of 0 Hz (Hz) or more and 100 Hz or less. At this time, the AC component of the detection signal in the present embodiment may also include components with a frequency exceeding 100 Hz. In addition, the DC component of the detection signal in the present embodiment may also include components with a frequency of 0 Hz or more and 1000 Hz or less, and at this time, the AC component of the detection signal in the present embodiment may also include components with a frequency exceeding 1000. In the present specification, the following is assumed to be: the DC component of the detection signal includes a component with a specified frequency of 0 Hz (Hz) to 100 Hz or more, and the AC component of the detection signal includes a component with a frequency band larger than the frequency band of the DC component to illustrate the present embodiment.

[0075] Through the research of the present inventors, it is known that the power consumption consumed in the signal processing may increase due to the detection signal output from the sensor and input to the signal processing circuit, and the signal processing performed on the detection signal. For example, it is known that when a magnetic sensor is used as a sensor to perform signal processing on the detection signal output from the magnetic sensor, an alternating current magnetic field (AC magnetic field) is superimposed on the magnetic field signal of the direct current magnetic field (DC magnetic field), and the alternating current component (AC component) of the magnetic field signal and the direct current component (DC component) of the magnetic field signal are input to the magnetic sensor unit together, if signal processing is performed on the magnetic field signal in which the AC component and the DC component are superimposed, the power consumption required for the signal processing may increase.

[0076] Figure 7 : shows an example of a signal waveform of a magnetic field signal processed by the magnetic sensor unit in this case. Figure 7 As shown, for example, a magnetic field signal having an AC component with a period T1 superimposed on a DC component is input. For example, when amplifying a magnetic field signal having AC and DC components superimposed thereon, power consumption may be three times or more than when amplifying only the DC component.

[0077] For example, in an information processing device or information equipment that transmits information using a sensor, more information can be transmitted by superimposing not only the DC component but also the AC component. However, if the frequency band of the signal is expanded, it may cause an increase in power consumption. For example, in a small portable information device, it is preferred not to increase power consumption.

[0078] In recent years, in order to increase the amount of information in portable information devices, the output signals to the signal processing circuit from various sensors provided in the information devices are sometimes increased by superimposing AC components on DC components. In addition, as the performance and functions of information devices are improved, more sensors are sometimes installed, and the amount of information from more sensors also increases. However, in particular, in portable information devices, from the perspective of battery consumption, it is preferred to suppress power consumption, and it is also preferred to suppress power consumption in the circuit that performs signal processing of the output signal from the sensor. For example, a magnetic sensor such as a compass is installed in a portable terminal, and sometimes it is particularly required to reduce the power consumption of the compass.

[0079] For example, when amplifying a detection signal input to a signal processing circuit, a telescopic amplifier circuit that can reduce relative power consumption compared to a folded cascode amplifier circuit is sometimes used as an amplifier circuit. However, since the telescopic amplifier circuit cannot increase the input voltage due to the limitation of the number of transistors that can be used, it is difficult to increase the detection signal input from the sensor. Therefore, in particular, in portable information devices, etc., a signal processing circuit that can increase the output signal from the sensor and suppress the increase in power consumption is desired.

[0080] Therefore, the inventors of the present invention separated the magnetic field signal (an example of the detection signal S) by using a separation circuit 22, that is, extracting the DC component by a low-pass filter 22a (LP: (Low pass)) and extracting the AC component by a high-pass filter 22b (HP (High pass)), thereby separating the detected magnetic field signal, thereby reducing the power consumption of the signal processing of the detection signal S, and were able to conceive of a signal processing circuit 20 of an embodiment of the present disclosure.

[0081] That is, as referenced Figure 6 As described above, the signal processing circuit 20 of the sensor unit 100 of this embodiment includes a low-pass filter 22a and a high-pass filter 22b. In the signal processing unit 20, the detection signal S output from the magnetic detection unit 10, which includes a DC component and an AC component, is extracted by the low-pass filter 22a and the AC component is extracted by the high-pass filter 22b.

[0082] Fig. 8A The frequency characteristics of an input signal in which an AC component is superimposed on a DC component are schematically shown. Figure 8B represents the frequency characteristics of the separated DC component, Figure 8C It represents the frequency characteristics of the separated AC component. Fig. 8A , Figure 8B and Figure 8C As shown in FIG. 1 , a signal with a large amplitude is observed in a relatively high frequency band (e.g., several hundred to several thousand Hz). Fig. 8A), in the signal processing circuit 20 of this embodiment, the DC component ( Figure 8B ) (in this embodiment, for example, a frequency band below 100 Hz), the AC component is extracted by the high-pass filter 22b ( Figure 8C ) (In this embodiment, for example, a frequency band above 100 Hz).

[0083] The extracted DC component and AC component are subjected to signal processing such as in subsequent steps. Figure 6 As shown, the signal processing circuit 20 may include, for example, a first amplifier circuit 24a (also referred to as a "first signal processing unit" in this embodiment) and a second amplifier circuit 24b (also referred to as a "second signal processing unit" in this embodiment), wherein the separated DC component is amplified by the first amplifier circuit 24a (first signal processing in this embodiment), and the separated AC component is amplified by the second amplifier circuit 24b (second signal processing in this embodiment). Compared with a case where a signal processing such as amplification is performed on an input signal having an AC component superimposed on a DC component without separation, the power consumption of the signal processing such as amplification performed in this case can be reduced.

[0084] In the signal processing circuit 20 of this embodiment, the separated DC component and AC component of the detection signal S may be added together. Fig. 9 As shown, the signal processing circuit 20 of this embodiment may also include an adding circuit (signal adding section 26), and may add the DC component extracted by the low-pass filter 22a and the AC component extracted by the high-pass filter 22b. In the subsequent signal processing of the added signal, compared with the case where the input signal in which the AC component is superimposed on the DC component is processed without separating, the power consumption can be reduced.

[0085] exist Fig.10 In FIG. 2 , it is shown that the DC component ( Figure 8B ) and AC component ( Figure 8C ) frequency characteristics of the signal added. Fig.10 As shown, the added signal covers the frequency bands of DC component and AC component. Fig. 8A The same frequency characteristics of the signal before separation are shown.

[0086] In addition, Fig. 9, the case where the DC component amplified by the first amplifier circuit 24a (i.e., the first output signal output by the first signal processing unit after the first signal processing is performed) and the AC component amplified by the second amplifier circuit 24b (i.e., the second output signal output by the second signal processing unit after the second signal processing is performed) are added by the adding circuit 26 is illustrated, but in the signal processing circuit 20 of this embodiment, the DC component and the AC component before the signal processing such as amplification are performed may be added. That is, the DC component output by the low-pass filter 22a and the AC component output by the high-pass filter 22b may be added.

[0087] In the signal processing circuit 20 of this embodiment, correction processing may also be performed on the added signal (also referred to as "added signal" in this embodiment). Fig.11 As shown, the signal processing circuit 20 of the present embodiment may include a correction circuit (signal correction section 28) for correcting the signal added by the signal adding section 26, and may perform the correction processing shown below.

[0088] exist Fig.12 , ideal characteristics of the magnetic detection unit 10 are shown. Fig.12 For example, the ideal characteristic of the magnetic detection unit 10 with respect to the X-direction component of the external magnetic field is shown. Fig.12 In FIG. 1 , the horizontal axis represents the intensity B of a component in a certain direction (for example, the X-direction component) of the external magnetic field, and the vertical axis represents the X-direction component (Sx) of the detection signal output by the magnetic detection unit 10. Fig.12 In the example shown, when the direction of the X-direction component of the external magnetic field is the +X direction, the intensity B is represented by a positive value, and when the direction of the X-direction component of the external magnetic field is the -X direction, the intensity B is represented by a negative value. Fig.12 In the example shown, the value of the detection signal S is 0 when the intensity B is 0, is positive when the intensity B is positive, is negative when the intensity B is negative, and increases when the intensity B increases. Fig.12 As shown, ideally, the detection signal S generated by the magnetic detection unit 10 is proportional to the intensity B of the external magnetic field.

[0089] However, depending on the environment in which the sensor unit 100 is used, etc., the magnetic detection unit 10 may show different Fig.12 The characteristics shown are different from the characteristics shown. For example, the magnetic field in the direction other than the X-axis direction of the external magnetic field sometimes affects the detection signal of the magnetic detection unit 10. In this case, the characteristics relative to the magnetic field strength are deformed, and sometimes the slope of the magnetic detection characteristics changes depending on the strength B of the external magnetic field.

[0090] Fig.13 This shows the characteristics of the magnetic detection unit in an undesirable situation. Fig.13As shown, in a non-ideal state, for example, when the strength B of the external magnetic field increases or decreases, the slope of the magnetic detection characteristic with respect to the strength B of the external magnetic field may decrease. Therefore, the detection signal S may not be proportional to the strength B of the magnetic field.

[0091] In this embodiment, for example, the correction may be performed as follows Fig.12 For example, the correction process may be performed so that the magnetic field intensity B and the detection signal S become proportional to each other.

[0092] In this embodiment, as described below, the correction value applied in the correction process may be calculated using the DC component of the detection signal. In addition, the correction value may be calculated using the DC component of the detection signal, for example, in a test field as an ideal environment.

[0093] As described above, the characteristics of the detection signal of the magnetic detection unit 10 with respect to the magnetic field strength are deformed. Fig.13 The slope of the change of the detection signal with respect to the magnetic field strength shown in FIG. 1 sometimes changes depending on the magnetic field strength. Assuming that the detection signal contains only a DC component, it is considered that: for example, in an ideal environment, the detection signal with respect to the change of the external magnetic field strength is proportional to the change of the external magnetic field strength, as shown in FIG. Fig.12 Therefore, in this embodiment, by using the correction value calculated using the DC component of the detection signal, it is possible to correct the deformation of the slope of the change of the detection signal with respect to the magnetic field strength.

[0094] In addition, for example, the scale of the amplitude of the AC component of the detected magnetic field signal is sometimes smaller than the scale of the amplitude of the DC component (for example, the scale of the amplitude of the AC component is one-tenth of the DC component or less). In this case, in the correction processing of the AC component of the detection signal, by using the correction value calculated based on the DC component to perform the correction processing, it is also easier to make the characteristics represented by the relationship between the above-mentioned magnetic field intensity B and the detection signal S close to the ideal state compared to the case of applying the correction value calculated based on the AC component.

[0095] In addition, for example, in the magnetic signal detected by the magnetic detection unit 10, an offset may be generated due to factors other than the magnetic field as the detection object. For example, when the magnetic field generated by a magnetic generator (not shown) is detected by the magnetic detection unit 10, an offset may be generated due to factors other than the magnetic generator. In this case, a correction value for correcting the offset may be calculated, and the signal correction circuit 28 may perform correction processing.

[0096] In the above-mentioned embodiment, the sensor unit 100 of this embodiment may be formed by forming the magnetic detection unit 10 and the signal processing circuit 20 separately and sealing them with resin or the like, or may be formed integrally (monolithically) with the magnetic detection unit 10 and the signal processing circuit 20. In the sensor unit 100 formed by any method, the above-mentioned effects are achieved.

[0097] In addition, in the above-mentioned embodiment, the sensor unit 100 having one magnetic detection unit 10 is described as an example, but the present embodiment can also be applied to the case of having multiple magnetic detection units 10, and in this case, the same effect as the above-mentioned effect is achieved. For example, the present embodiment can also be applied to the case of having multiple magnetic detection units with the same magnetic sensitivity direction as the magnetic detection unit 10, the case of each having a magnetic detection unit with a different magnetic sensitivity direction, the case of each having multiple magnetic detection units with different magnetic sensitivity directions, etc. In this way, when there are multiple magnetic detection units and the signal processing circuits connected to each magnetic detection unit are increased, the power consumption sometimes increases with the increase of the signal processing circuits. As described above, since the power consumption can be reduced by the present embodiment, the present embodiment can be effectively applied to the sensor unit 100 having multiple magnetic detection units and increased power consumption.

[0098] The above-described embodiments are intended to facilitate understanding of the embodiments of the present invention, and are not intended to limit the interpretation of the embodiments of the present invention. The various elements and their configurations, materials, conditions, shapes, and sizes of the embodiments are not limited to the examples and can be appropriately changed. In addition, the structures shown in different embodiments can be partially replaced or combined with each other.

[0099] For example, the sensor unit 100 of the present embodiment can be applied to a magnetic sensor unit, and when used as a magnetic sensor unit, it can also be used to detect position changes in the XY plane or in the Z direction based on changes in the magnetic field in the Z direction. Applications of the sensor include, for example, strain gauges, angle sensors, position sensors, compasses, current sensors, switches, etc., as well as actuators for robot joint mechanisms, opening and closing detection mechanisms for laptop computers, joysticks, brushless motors, magnetic encoders, and other electronic devices.

Claims

1. A signal processing circuit, wherein: Processing of detection signals output from sensors that contain DC and AC components: a low-pass filter that extracts the DC component from the detection signal; and A high pass filter extracts the AC component from the detection signal.

2. The signal processing circuit according to claim 1, wherein: The device includes a signal adding unit that adds the DC component extracted by the low-pass filter and the AC component extracted by the high-pass filter.

3. The signal processing circuit according to claim 2, wherein: The device further includes a signal correction unit configured to correct the added signal by applying a correction value calculated based on the DC component to the added signal, which is an output signal from the signal adding unit.

4. The signal processing circuit according to claim 1, wherein: have: a first signal processing unit that performs a first signal processing on the DC component; and The second signal processing unit performs second signal processing on the AC component.

5. The signal processing circuit according to claim 4, wherein: The device includes a signal adding unit that adds a first output signal, which is an output signal from the first signal processing unit, and a second output signal, which is an output signal from the second signal processing unit.

6. The signal processing circuit according to claim 5, wherein: The device further includes a signal correction unit configured to correct the added signal by applying a correction value calculated based on the DC component to the added signal, which is an output signal from the signal adding unit.

7. The signal processing circuit according to claim 1, wherein: The sensor is a magnetic sensor.

8. A sensor unit, wherein: have: the sensor; and The signal processing circuit of claim 1 is formed integrally with the sensor.

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